The present invention relates to a re-sealable packaging, which can be readily opened and then re-sealed or re-closed.
This type of packaging, with a flexible lid or cover able to be re-closed over the container is known, notably in the food industry, both for packagings under gas employing a rigid receptacle (heat-molded or preformed, for example by injection molding) as well as for vacuum packagings with a heat-molded flexible receptacle.
Thus, British Patent application 2,319,746 (in the name of Dolphin) discloses heat-weldable films for re-closable packagings. This packaging comprises a receptacle (A) comprising a support layer (for example in PVC or PET), a layer in PE and a thin film in an isomer resin or in ethylene/methyl acrylate copolymer, and a flexible lid (B) comprising a layer in ionomer or copolymer identical to the preceding layer, with which it co-operates, and a layer of elastomer adhesive, a layer of PE and a support layer (in PVC, PET). In this structure, welding is effected by means of the ionomer resin or ethylene and/or methyl acrylate copolymer, the films (A) and (B) being situated between the sealing jaws, only the upper sealing jaw being heated.
This structure is only functional due to the fact that the ionomer resin or copolymer has a low melting point (and notably less than that of the adhesive layer).
A similar structure is disclosed in international application WO-A-90 07427 (in the name of James River), additionally cited in the above-said Patent application in the name of Dolphin. The structure described in that James River application is adapted to production of flexible bags. The structure comprises a support layer, a layer in an elastomer adhesive, and a xe2x80x9cskinxe2x80x9d, this xe2x80x9cskinxe2x80x9d being heat-weldable. This xe2x80x9cskinxe2x80x9d is preferably an ionomer resin or a copolymer of the same type as those disclosed in the above patent application in the name of Dolphin. This structure is welded to itself during manufacture of the bags. At the time of opening, delamination can occur at the adhesive/skin interface or the adhesive/support layer interface or within the adhesive itself. In this latter case of delamination, the sealing jaws between which the structure is welded are both heating jaws.
U.S. Pat. No. 3,454,210 discloses a packaging comprising a container and a lid, this lid comprising e.g. a PET layer, a Corona-treated PE, an adhesive layer and a weldable PE layer. It is furthermore indicated, but without any full disclosure, that the re-sealable film can also be present on the container.
The above packagings have various disadvantages. Firstly, they are not designed to be employed in all types of packaging, whether xe2x80x9cunder gasxe2x80x9d or xe2x80x9cunder vacuumxe2x80x9d, whether rigid or flexible, notably flexible bags, and in all types of machine, whether horizontal or vertical. One consequently looks for a xe2x80x9cuniversalxe2x80x9d structure able to be adapted to existing machines, and finding general application. Finally, such packagings require, for the heat-weldable layer, the use of ionomer resins which are extremely costly, which makes the final packaging relatively expensive.
None of the above documents teaches nor suggests the invention.
Thus, the invention provides a re-closable packaging comprising:
(A) a container, said container comprising a support layer (1), a pressure-sensitive adhesive layer (3) and a tearable welding layer (4); and, facing said container,
(B) a cover member or lid, said cover member comprising a welding layer (5) and a support layer (6),
said tearable welding layer (4) and said welding layer (5) being welded along a seam (D).
According to one embodiment of the re-closable packaging, the pressure-sensitive adhesive layer (3) is applied directly to said support layer.
According to another embodiment of the re-closable packaging, a complexable layer (2) is arranged between said support layer (1) and said pressure-sensitive adhesive layer (3).
According to one embodiment of the re-closable packaging, a structure (C) comprising layers (2), (3) and (4) is laminated onto said support layer (1).
According to a further embodiment of the packaging, said container (A) is a rigid tub or receptacle.
According to a further embodiment of the packaging, said container (A) is a flexible receptacle.
According to a further embodiment of the packaging, said container (A) is thermoformed.
The invention further provides a re-closable packaging of a second type comprising:
(A) a container, said container comprising a support layer (1), a complexable layer (2), a pressure-sensitive adhesive layer (3) and a tearable welding layer (4); and, facing the tearable welding layer of (A) is the container
(Axe2x80x2), that container comprising a support layer (1xe2x80x2), a complexable layer (2xe2x80x2), a pressure-sensitive adhesive layer (3xe2x80x2) and a tearable welding layer (4xe2x80x2) where the tearable welding layer (4xe2x80x2) of (Axe2x80x2) faces the tearable welding layer (4) of (A);
said tearable welding layers being welded along a seam (D).
According to one embodiment of the second type of re-closable packaging, said containers form the same structure closed about itself.
According to one embodiment of the second type of re-closable packaging, said containers are flexible films.
In a further embodiment of the re-closable packaging, tearing at said seam takes place within said adhesive layer (3).
In a further embodiment of the re-closable packaging, the melting point of the said tearable welding layer is higher than that of said adhesive layer. The term xe2x80x9cmelting pointxe2x80x9d as regards the adhesive is intended to mean its softening point.
According to a further embodiment of the packaging, said pressure-sensitive adhesive layer comprises a thermoplastic elastomer-based hot melt adhesive.
According to yet a further embodiment of the packaging, said adhesive comprises from 5 to 25% by weight filler-containing master batch.
According to a further embodiment of the packaging, said welding layers comprise polyethylene.
According to one embodiment of the re-closable packaging, said tearable welding layers comprise metallocene PE.
The complexable layers and tearable welding layers preferably have identical compositions.
In a further embodiment of the re-closable packaging, said structure comprising said layers (2), (3) and (4) is symmetrical in composition, said pressure-sensitive adhesive layer (3, 3xe2x80x2) comprising two pressure-sensitive adhesive sub-layers.
According to one embodiment of the re-closable packaging, said structure is obtained by collapsing the co-extrusion bubble.
According to one embodiment of the re-closable packaging, collapsing the co-extrusion bubble is done under oxidizing conditions.
The invention also provides a method for producing a packaging according to the invention, comprising sealing said welding layers (4) and (5).
In one embodiment of the method, said structure, comprising said support layer (1), said complexable layer (2) and said pressure-sensitive adhesive layer (3) is prepared first after which said container is prepared.
In one embodiment of the method, said structure is laminated onto said container.
In another embodiment of the method, said structure is prepared by collapsing the co-extrusion bubble.
In one embodiment of the method, for producing a packaging, said support layer (1), pressure-sensitive adhesive layer (3) and tearable welding layer (4) are prepared by co-extrusion or by calendering.
Sealing is preferably done, for preparing a packaging of the first type, by die pressing between two sealing jaws only one of which is heated at said lid or cover member (B) side.
For preparing a packaging of the second type, sealing is preferably done by die pressing between two sealing jaws only one of which is heated.
The invention will now be described in more detail below, with reference to the attached drawings.